Glad you asked. So technically you can write on ANY part of the timeline. The past the present, or even the future
The current century is the 20th century, which the present year is year 2400 for them. But overall.
If you write a story in the past, just make sure it doesn't intervene with the present, so nothing too destructive.
If you write a story in the future, you have to atleast make reference to the present of the past. Not alot, just atleast once.Like a major event that happened during those timeleines, like a huge war that just ended.
There overall is no main focusing story, but there will be main or leading plot lines in the series, which take the form of character arcs for major characters in the series, (Which you can also make)
But thus far due to nothing being included yet, there currently is no official timeline as of yet. but if you want I can include some events to be included and give you somewhat of a setting for what goes on. So yeah, most of the stuff will come as more people contribute to it.